Conventional size reduction equipment for granulating plastic materials commonly include as essential elements a so-called barrel or cutting chamber within which a rotor is mounted for rotation on a support shaft. Knives are fixed coaxially on the surface of the rotor and upon rotation of the rotor the rotor knives rotate in close proximity to one or more stationary bed knives secured within the cutting chamber. Plastic material fed into the cutting chamber is comminuted by the cooperative effect of the moving rotor knives and the stationary bed knives.
The usual method of feeding plastic material into the cutting chamber is by conveying the material into a stationary chute through which the material is free to fall by gravity through an opening at the top of the cutting chamber. While this technique works well in conventional industrial applications it is not acceptable in certain environments, one being where light weight containers with cylindrical configuration could bounce around freely without being engaged by rotating knives against fixed bed knives.
In the promotion of environmental interests it is becoming increasingly popular for plastic containers such as beverage bottles to be returned by the customer to the point where the containers are sold or other collection center where the containers are gathered for ultimate delivery to a location where they are comminuted and the resultant plastic particles recycled. Recent techniques have contemplated that the consumer returning the used plastic containers would feed them into a device at the collection center which may be the point of purchase, perhaps being rewarded by receiving a deposit fee automatically as each plastic container is fed into the granulation system. Since it will be appreciated that these steps represent the reverse of inserting a coin or coins into a vending machine to obtain a beverage, for example, the system of plastic reclamation here under discussion is sometimes called "reverse vending".
Typically reverse vending is carried out at locations wherein the plastic containers are sold. This dictates that the reversing vending machine must be safe to operate, consume a minimum amount of floor space, granulate to reduce bulk density, avoid any inadvertant discharge of the granulated plastic out of the granulator, be simple in operation and be completely reliable in use. The present invention admirably fulfills all of these objectives.